1. Field of the Invention
The present invention relates to an image display and, more particularly, to a control apparatus and method for an image display having an ABL (Auto-Brightness Limitation circuit).
2. Related Background Art
Some image displays comprise ABLs (Auto-Brightness Limitation circuits) for limiting the display brightness. The ABL generally suppresses and controls the average display brightness of the screen so as not to excessively increase it for the purpose of suppression of power consumption or the like. The control response speed is preferably higher in terms of suppression of power consumption. However, an excessively high speed makes the display brightness of the screen unstable when the average brightness changes between frames (fields) of the same scene. The display brightness is generally controlled with a response slowed down with a given time constant.
With such a slow response, control is performed with a delay after the image brightness changes when, for example, the image brightness greatly changes within a short period upon a scene changeover. No control is done immediately when the image brightness changes greatly. The image brightness gradually changes with a delay. Such a change of the brightness gives the image observer a visual sense of incongruity or incompatibility.
To solve this problem, the present applicant has proposed an image display control apparatus as disclosed in Japanese Laid-Open Gazette No. 2000-250463. In this Gazette, there is disclosed a control apparatus and method for an image display that can suppress any increase in power consumption and heat generation on the display surface by controlling the display brightness in response to a change of a video signal, and also prevent any visual sense of incongruity or incompatibility by control.
In this Gazette, in order to detect the frame correlation, the sum of the absolute values of differences between frames of a color difference signal for each block prepared by dividing the display area must be calculated, resulting in a large-scale processing circuit.
The present invention has been made to overcome the conventional drawbacks, and has as its object to provide a control apparatus and method for an image display that can suppress any increase in power consumption of the image display and heat generation on the display surface by controlling the display brightness in response to a change of a video signal, prevent any visual sense of incongruity or incompatibility by control, and suppress any increase in circuit scale.